In some hemodialysis devices, the clearance of toxins occurs through diffusion. While diffusion-based clearance can be effective at removing small molecules, larger toxins are not removed as effectively because they diffuse more slowly. The clearance of toxins may also occur through convective clearance. Convective clearance is not heavily affected by molecular size, and therefore removes toxins of all sizes as long as they fall below the cut-off of the filtration membrane. However, convective clearance results in fluid loss from the blood. The loss of fluid from the blood creates a greater concentration of blood cells and proteins within the remaining blood fluid which in turn increases the likelihood of clotting and other damage to the blood cells.